1. Technical Field
The present invention relates to a variable wavelength interference filter for selectively emitting light with a desired target wavelength out of the incident light, an optical module equipped with the variable wavelength interference filter, an electronic apparatus equipped with the optical module, and a method of manufacturing a variable wavelength interference filter.
2. Related Art
In the past, there has been known a spectral filter, which reflects light between a pair of mirrors to transmit light with a specific wavelength while canceling out lights with other wavelengths each other due to interference, to thereby obtain the light with the specific wavelength out of the incident light. Further, as such a spectral filter, there has been known a variable wavelength interference filter, which selectively emits the light to be emitted by controlling the distance between the mirrors (see, e.g., JP-A-62-257032 (Document 1)).
The variable wavelength interference filter described in Document 1 is equipped with a stationary mirror provided to a light transmissive substrate, and a movable mirror disposed so as to be opposed to the stationary mirror. The variable wavelength interference filter drives the movable mirror with an electrostatic attractive force to thereby control the distance between the mirrors, and thus selects the light to be emitted.
There is a concern that such a variable wavelength interference filter is deteriorated in drive characteristics and optical characteristics due to an environmental factor such as moisture or foreign matters, and is thus degraded in reliability. Therefore, there has been known a method of airtightly encapsulating the variable wavelength interference filter in a package in order to improve the reliability of the variable wavelength interference filter (see, e.g., JP-T-2005-510756 (Document 2).
The package described in Document 2 is provided with a header, a plurality of electrically-conductive pins, and a cap having an optical window, and forms an inside space incorporating the variable wavelength interference filter therein, and airtightly sealed with the cap and the header.
However, in the case of the package described in Document 2, it is necessary to prepare the package separately from the variable wavelength interference filter, and assemble each of the components separately. Therefore, in order to ensure the reliability of the variable wavelength interference filter, a lot of cost and time is required for the package, as a separate component, and the assembling of the package. Further, since the package as a separate component has walls for housing the variable wavelength interference filter and airtightly sealing the periphery of the variable wavelength interference filter, there is a problem that the size of the variable wavelength interference filter including the package increases.